1. Field of the Invention
The present invention relates to a silicon-on-insulator (SOI) substrate, a manufacturing method thereof, a semiconductor device using the SOI substrate, and a manufacturing method thereof.
2. Description of the Related Art
In recent years, integrated circuits using a silicon-on-insulator (SOI) substrate where a thin single crystal semiconductor film is present over an insulating surface, instead of using a bulk silicon wafer, have been developed. Because parasitic capacitance between a drain of a transistor and a substrate is reduced by use of an SOI substrate, SOI substrates are attracting attention as substrates which improve performance of semiconductor integrated circuits.
One of known methods for manufacturing SOI substrates is a Smart Cut® method. A summary of a method for manufacturing an SOI substrate by a Smart Cut method is described below. First, by implantation of hydrogen ions into a silicon wafer serving as a substrate for separation by an ion implantation method, an ion-implanted layer is formed at a predetermined depth from the surface. Next, the silicon wafer into which hydrogen ions are implanted is bonded to another silicon wafer with a silicon oxide film interposed therebetween. Then, through heat treatment, the ion-implanted layer serves as a cleavage plane and the silicon wafer for separation into which hydrogen ions are implanted is separated to be a thin film. Accordingly, a single crystal silicon film can be formed over the silicon wafer for separation. The Smart Cut method may also be referred to as an ion implantation separation method.
A method for forming a single crystal silicon film over a supporting substrate made of glass by using such a Smart Cut method has been proposed (e.g., see Reference 1: Japanese Published Patent Application No. 2004-87606).